Vinegar (Acetic acid fermentation)
The world 'vinegar' is derived from the French term 'vinaigre' (vin = wine + aigre = sour), meaning "sour wine". It contains about 40% acetic acid by weight and small quantities of alcohol, glycerol, easters, sugars, and salts. Vinegar is the product obtained as a result of impartial oxidation of alcohol in a fermenting sugar containing fruit or cane juice, molasses, fermented mash of malted grain, honey, maple skimmings, syrups, etc. Since, the vinegar contains considerably large amount of acetic acid it is generally used in the place if acetic acid. But, to find pure acetic the vinegar is subjected to purification.
Reaction. The fermentation of vinegar involves two types of biochemical reactions:
(i) Alcoholic fermentation of carbohydrate. It is the first step in the production of vinegar and takes place under anaerobic condition. This step in which sugar is fermented to alcohol is completed by the action of yeast species.
(ii) Oxidation of alcohol to acid. This is the second in the production of vinegar and is aerobic process. This step in which alcohol is oxidised to acetic aci8d is completed by the action of acetic bacteria, i.e., the species of Acetobacter, namely orleansis, A., A. schulzenbachi,